Engine for outboard engine system

Abstract

A cylinder head is coupled to a cylinder block/cylinder head coupling surface of a cylinder block by ten bolts which are disposed to surround outer peripheries of cylinders. In order to enhance sealability of an opening of an oil passage defined radially outside the bolts as viewed from the cylinders, the cylinder block and the cylinder head are further fastened to each other by two bolts disposed in the vicinity of the opening. Thus, the fastening force of the cylinder block/cylinder head coupling surface can be increased to increase the degree of freedom in design of the opening of the oil passage defined in the coupling surface.

What is claimed is: 
     
       1. An engine for an outboard engine system, comprising a cylinder head coupled to a cylinder block by a plurality of first coupling bolts disposed at substantially equal distances from a cylinder axis so as to surround an outer periphery of a cylinder, and an oil passage having an opening which is defined in a cylinder head/cylinder block coupling surface at a location radially outside said first coupling bolts as viewed from the cylinder axis, wherein said cylinder head is fastened to said cylinder block by second coupling bolts disposed radially outside said first coupling bolts as viewed from the cylinder axis in the vicinity of the opening of said oil passage.   
     
     
       2. An engine for an outboard engine system according to claim 1, further including an opening of a cooling water passage, which is defined in said cylinder head/cylinder block coupling surface, and one of said second coupling bolts is disposed between the opening of said cooling water passage and the opening of said oil passage.